Current Green Chemistry - Volume 2, Issue 4, 2015

Design of composite biosorbents based either on polysaccharides as biopolymer matrix embedded with natural or synthetic zeolites or composite hydrogels having polysaccharides as one component and their applications in sorption processes of heavy metal ions and dyes has been reviewed based on the most recent publications in the field. It was demonstrated that polysaccharide-zeolite composites exhibit higher performance in sorption of environmental pollutants comparative with natural or synthetic zeolites or pristine biopolymers. The polysaccharide-zeolite composites are economically feasible because they are easy to prepare and involve inexpensive chemical reagents, which are coming from renewable resources. On the other hand, the polysaccharide based composite hydrogels present stiffer and tougher mechanical properties and more efficient sorption/desorption properties compared to conventional hydrogels. Interpenetrating polymer network composite hydrogels based on chitosan, alginate, starch, cellulose, and other polysaccharides, reported mainly in the last decade, and their sorption properties for heavy metal ions and dyes are discussed in this review.

Inorganic antimicrobial agents have attracted increasing attention as they can overcome the shortcomings of organic antimicrobial agents, such as low heat resistance, high decomposability, and short life expectancy. Typical examples of inorganic antimicrobial agents are titania, zinc oxide, silver, and metal-exchanged zeolites. Silver- or zinc-ion-exchanged synthetic zeolites are known to exhibit antimicrobial activities in which zeolites are used as a carrier for silver or zinc oxide. The particle size and color shade of synthetic zeolites can be well controlled compared to those of natural zeolites. Even though natural zeolites exhibit limitations with respect to the color and have relatively lower cationexchange capacity than that of synthetic zeolites, they can be effective as antimicrobial agents after active metal exchange. The antimicrobial activity and deodorization effects are compared; further, the possibility of the decomposition of volatile organic compounds by incorporating photocatalytic materials in the antimicrobial agent of cation-exchanged zeolite was investigated for the application to textiles. Various applications of biomedicine, food package, textile, and building interior materials in the form of coatings, films, and polymer composites were also summarized.

The topic of this paper is to review some results of laboratory examinations of mostly volcanic aluminosilicates (clinoptilolite-rich tuffs, tephra, stilbite, alginite, montmorillonite, perlite product vapex) deposited in Slovak and some Chinese repositories, which were achieved during scientific cooperation. The overview is limited and highlights only those results which concern Pb(II), Al(III), PO4 3- and Sb species removal from aqueous solutions and also compares other pollutants such as nitrate, sulphate, azodyes and cefazoline using the above adsorbents. The paper reports several synthesis routes, by which naturally available minerals or even waste products (furnace slag), occur in both cooperating countries in vast quantities and have been combined with specific biogenic components (like surfactant, alginate and xanthan gum) in order to prepare novel functional gradient adsorbents suitable for economically and ecologically viable water decontamination. Additionally, Fe-modified zeolite and the German commercial product GEH as well as the Czech Nanofer 25S in the form of stabilized aqueous suspension of Fe(0) were used in the experiments to compare the adsorption efficiency of the above materials.

In this review attention is focused on the various traditional and ecofriendly adsorbents, including a few of the local repositories which have proven enhanced performance for environmental pollutants removal. Due to their low cost and local availability, natural materials such as zeolite, montmorillonite-rich bentonite, industrial waste product chezacarb, beringite, chitosan, low rank coal shungite, fossil alginite, slovakite, starch, peat, commercial-grade active coke and iron oxihydroxides GEH were chosen to evaluate their adsorption performance in selected pollutant removal. A mathematical evaluation and fundamental aspects of the adsorption process are discussed respectively. The maximum adsorption capacity of ODA-zeolite towards oxyanionic sulphate, chloride and nitrate reached the values 7-9 mg/g, while the maximum adsorption capacity of Fe(III)alginate zeolitic pellets towards nitrate reached the value 44 mg/g. Adsorption isotherm for phenol onto carbonized zeolite did not proceed according to the standard isotherm shape whereas the first plato recorded the maximum capacity even around 100 mg/g.

The Pd-catalyzed P–C couplings of aryl, hetaryl and vinyl derivatives and species with a P(O)H function, typically dialkyl phosphites and secondary phosphine oxides giving rise to phosphonates and phosphine oxides are summarized with special emphasis on the green chemical variations. A great variety of reactions are discussed to demonstrate the different conditions and catalyst systems described. environmentally friendly protocols include the use of a phase transfer catalyst and the microwave technique. The best way is to perform the P–C coupling reactions under Pligand- free and solvent-free conditions.

Fatty-acid methyl esters (FAME) are considered a renewable source of raw materials for the chemical industry, including their use in biodiesel fuel mixtures. In the following manuscript, we describe the cross-metathesis reactions of a corn oil-derived FAME mixture with isobutylene and other branched light olefins. Cross-metathesis reactions are also reported with styrene. Cross-metathesis reactions were done with methyl oleate as a reference. These reforming reactions were done in an effort to increase the volatility of the fuel mixtures, as well as introduce branching or the phenyl group into the hydrocarbon chains. The resulting metathesis products contain high percentages of biorenewable carbon (46-100%). The chemistry represents a new approach to the preparation of green fuels - as a biorenewable stream is merged with high volume petroleum-derived streams.

Ethyl lactate, a bio-based nontoxic solvent has been found as a medium for the general synthesis of keto- and aldoximes under catalyst-free conditions. The synthesis of amides via Fe-catalyzed Beckmann rearrangement of the ketoxime has also been realized in the same green medium.

Microwave irradiation was used to promote the synthesis of functionalized homoallylic alcohols from the reaction of the appropriate aldehydes and potassium allyltrifluoroborate. The products were obtained in good yields in a short reaction time at 80 ^oC using a minimum amount of water as the reaction solvent without any catalyst.